I suggest creating games named "EA nations", "MA nations" etc. Create a new game, choose a big map, press 'n' until no more nations are added, press 'shift+H' to turn all nations to human. Press and hold enter, and click "ready" whenever a pretender pops up. It will only take about 10 seconds or so, bit more until the game is created, but that way you can quickly view all nations of the game.
There's also an
AllView map, which I recently updated. To get it to work properly, you have to enable a mod that adds a new unit with high unit ID, but it will also work for the next patch. If you haven't tried any mods out yet, it isn't a big deal - you'll be unable to view about 3 units, out of nearly 2000.